The disclosure relates to a fuel tank, which has a vent line from a hydrocarbon filter element to a fresh air filter.
Fuel tanks usually have a plurality of lines, for example, a filling line, a vapor purge line and the vent line from the hydrocarbon filter element to the fresh air filter. Such fuel tanks with the associated line system are sufficiently known, for which reason they will not be examined in any further detail here.
The hydrocarbon filter element is embodied as an activated charcoal filter, for example, and is intended, for example, to filter hydrocarbons out of fuel gases, so that these cannot get into the surroundings. For this purpose the hydrocarbon filter element is arranged between the fuel tank and the fresh air filter of the internal combustion engine, for example.
An example fuel tank with associated line system is disclosed in U.S. Pat. No. 7,481,101 B1. A vacuum-generating pump module, which comprises a control valve and a bypass, is arranged between an activated charcoal filter and the atmosphere. Bores are made in the control valve. In a state which is termed the “OFF state”, the surroundings communicate via one of the bores with the inlet side of the activated charcoal filter. In an “On State”, on the other hand, the activated charcoal filter communicates via the other bore with a pump side. A closed system is thus disclosed, irrespective of whether the control valve is in its OFF or in its On state.
U.S. Pat. No. 5,651,349 also relates to a fuel tank with associated line system, U.S. Pat. No. 5,651,349 relating in particular to a method for monitoring a venting system and to the venting system itself. An activated charcoal filter is connected to the fuel tank on the one hand and to the internal combustion engine on the other. A valve is arranged on the activated charcoal filter in order to be able to admit air into the activated charcoal filter.
The fuel tank or the corresponding system is subjected to a leak test, especially on completion of the finished motor vehicle. This test is included in the so-called “end of line test”, that is to say as an integral part of the final acceptance of the motor vehicle by the manufacturer. In the inspection of the fuel tank with the connected line system, the vent line is separated from the hydrocarbon filter element. An external pressure-generating device is connected to the hydrocarbon filter element, so that a corresponding pressure test can be carried out, which indicates whether the fuel tank or the corresponding line system has any leaks. Such a pressure test is commonly known. If no leaks are detected, the vent line should be connected to the hydrocarbon filter element again, so that filtered fresh air can get into the fuel tank.
Despite the quality assurance systems introduced and practiced in the motor vehicle industry, however, it can happen, due to human oversight, that the vent line is not reconnected to the hydrocarbon filter element after successfully carrying out the pressure test. In such a case, in normal operation of the motor vehicle and of the internal combustion engine, unfiltered fresh air could pass through the hydrocarbon filter element into the fuel tank. Thus, for example, liquids or solids could get into the fuel tank, since there is no connection to the fresh air filter. Such contamination is obviously regarded as particularly harmful.